Silencer



Jan. 5, 1932. R B, BOURNE 1,839,462

S ILENGER Filed. May '7, 1929 IN V EN TOR.

@w A W ATTORNEYS.

Patented Jan. 5, 1932 UNITED STATES.

PATENT. OFFICE .nomnn 1a. BOURKE, F mrronn, como rrour, assrenon 'ro THE MAXIM srrnnonza Germany, or m'rronn, oonnnorrcnr, A oonroaarron or oonnnorrcor SILEN'CEB.

Application filed May 7, 1929. Serial No. 361,213. 7

The present invention pertains to silencing devices for the exhaust of gasoline engines and the like. This device, if cast in iron, is particularly adapted to installations where cooling water is fed from the engine into the exhaust pipe, as is common in marine practies.

The invention makes use of established acoustic principles for rendering inoifensive the complex exhaust noise connected with the discharge of gasoline engines. An attenuation of the relatively high frequencies is obtained by the acoustic resistance of narrow and curved passages. The medium and low 1 frequencies are attenuated by acoustic im- J pedances formed-by a. main channel and a side branch chamber in communication therewith. The range of frequencies attenuable by this impedance is materially extended through the presence of the resistance in the main channel. The resistance of a curved channel near its boundin surfaces, while suficient to satisfactorily dampen high frequencies, is insuficient to attenuate low frequency waves. As stated before, the efiect of the impedance is modified by the presence of the resistance.

One object of the invention is the attenuation of audible waves of a wide range of frequencies to a degree wherethey lose their offensiveness by means which permit at the same time the discharging of the gases without undue back pressure. Another object is to provide a small, compact, and inexpensive 5 device which may be made to withstand rough I usage and corrosive action of hot-sea water. Still other objects and advantages will appear in the subsequent detailed description.

In the preferred embodiment of the in 49 vention- Fig. 1 is an elevational cross-section of the device taken on line 11 of Fig. 2; and

Fig. 2 is a plan cross-section through line 2-2 of Fig. 1 y

The silencer. is preferably made of castiron whereby the advantages of. relatively cheap manufacture and resistance to corrosion are obtained. Referring to the drawings it will be noted that a cylindrical casing is formed by two separate portions. The

cup-shaped portion 15 has two integral flanged openings, one of them '3 axially at the bottom and the other 1 at the circumference. Both openings are shown as provided with bushings 4 and 2 respectively. Opening 1 is used as inlet and opening 3 as outlet for the gases and, if so used, for the cooling water as well. The cover-plate portion 16 is fastened to the cup by means of bolts 6 passing through the cover and the cup flange 5. A packing ring 17 provides a tight seal. Both portions 15 and 16 have cast integrally therewith interior curved webs 13, 14 and 11, 12 respectively, which. when the cover is attached to the cup, telescope and thereby form curved passages as can best be seen from Fig. 2. Tight closure for these passages with respect to the bottom and cover walls is secured by grooves 9 and 10 respectively with suitable packing material therein.

Looking at Fig. 2 it will be seen that the gas current entering the channel 18 divides into two parallel currents 19 and 20 continued in the channels 21' and 22, and reunited in the exit channel 23. The acoustic side chamber forming two lobes 24 and 25 is connected to the channels about midway thereof by gaps or slots provided between the webs 13, 14: and 11, 12, the gap 26 which is nearer to the side chamber being narrower than the more remote gap 27, in order to establish a better acoustic balance.

Acoustically, a system is thus created which consists of two about equally great resistancereactance combinations in series, each comprising two practically equal "resistance-reactance conduits in parallel formed by the surfaces and the gas volumes in the channels 19 and 20 and in the channels 21 and 22 re spectively.- This parallel-series combination is shunted about midway at 26 and 27 by a substantially reactive side branch element or impedance 24-25 having the form of a lobed and closed side chamber. Such a closed side chamber serves to attenuate a. group of medium and low frequencies, the width of the band of frequencies thus attenuated being dependent upon the size and shape of said closed side chamber, together with the acoustic characteristics of the acoustic channel or chanin the channels.

nels to which it is coupled. This effect, particularly in the higher frequency range, is materially assisted by frictional dampening The device, therefore, combines two acoustic means for sound attrition in order to obtain silencing elfects over a wide sound range without unduly impairing the easy flow of the exhaust gases.

In the drawings, a pair of parallel channels 19, 20 and 21, 22 is shown. There coiild also be provided a greater number of parallel passages, if it should be desired to further increase the frictional resistance. However, by casting part of the webs integral with the bottom of the cup and part of them integral with the cover and by telescoping these diverse webs it is possible to make the depth of the parallel channels very small and to provide a comparatively large contact surface or high resistance in them, whereby it is possible to employ but two passages in parallel.

It should be understood that other minor changes of the structure will be permissible, also the use of other material than cast-iron, without departing from-the scope of the in- Vention.

What I claim is:

1. Conduits arranged in parallel having a closed side branch chamber acoustically coupled thereto at a point intermediately along the length of said conduits.

2. Conduits arranged in parallel having a closed side branch chamber acoustically coupled thereto at a point essentially equi-distant from the ends of said conduits.

3. Curved conduits arranged in parallel having a closed side branch chamber acoustically coupled thereto at a point intermediately along the length of said conduits. V

4. Curved conduits arranged in parallel having a closed side branch chamber acoustically coupled thereto at a point essential- 1y equi-distant from the ends of" said conduits.

5. A silencer comprising a cylindrical casmg with an axial and a circumferential opening thereinto, curved conduits arranged in parallel connecting said openings, and a closed side branch chamber acoustically coupled to said conduits.

6. A silencer comprising a cylindrical casing with an axial and a circumferential opening thereinto, partitions in saidcasing forming curved parallel .channels in communication with said openings, and a closed I side branch chamber acoustically coupled thereto at a point intermediately along the length of said channels.

7. A silencer comprising a cylindrical casing with an axial and a circumferential opening thereinto, partitions in said casing forming curved parallel channels in communication with said openings, and a closed side branch chamber acoustically coupled to said I channels at a point essentially equidistant from the ends of said channels.

8. A silencer casing having an axial and a circumferential opening thereinto comprising a cup-shaped portion and a cover-plate portion fastened to said cup portion, curved webs integral with the cup-bottom and curved Webs integral with the cover-plate, said deverse webs, when the cover is attached to the cup, being in telescopic relation and in conjunction with said bottom and cover walls forming curved channels between the open ings, and a lobed chamber, the latter communicating as an acoustic side branch element with the channels by gaps in the webs.

9. A. silencer casing having an axial and a circumferential opening thereinto comprising a cup-shaped portion and a cover-plate portion fastened to said cup portion curved webs integral with the cup-bottom and curved webs integral with the cover-plate, said diverse webs, when the cover is attached to the cup, being in telescopic relation and in conjunction with said bottom and cover walls forming curved parallel channels between the openings, and a lobed chamber,

} the latter communicating as an acoustic side branch element the webs.

10. Conduits arranged in parallel, each conduit presenting a substantially continuous channel for gas flow, and an acoustic side branch element coupled acoustically to both of the conduits butpositioned out of the line of gas flow.

11. Conduits arranged in parallel, each conduit presenting a substantially continuous channel for gas flow, and a closed acoustic side branch elements coupled acoustically to both of the conduits but positioned out of the line of gas flow. v

12; Curved conduits arranged in parallel, each conduit presenting a substantially continuous channel for gas flow without abrupt changes in direction, and an acoustic side branch element coupled acoustically to both of the conduits but positioned out of the line of gas flow.

13. Curved conduits arranged in parallel, each conduit presenting a substantially continuous channel for gas flow without abrupt changes in direction, and a closed acoustic with the channels by gaps in side branch element coupled acoustically to signature.

ROLAIND B. BOURNE.

positioned out of the 

